1. Field of the Invention
This invention relates to multi-use hand trucks and especially to such hand trucks which can be used in a four wheel mode of operation for conveying heavy articles, a two wheel mode of operation as a conventional hand truck or in a stepladder mode of operation.
2. Description of the Prior Art
Various combined lifting and load moving devices have been known in the past. For instance, U.S. Pat. No. 107,225, issued Sept. 13, 1870, to Claflin, shows a stepladder having a platform which can be raised on the stepladder by connection to a pulley and winch arrangement. U.S. Pat. No. 2,514,825, issued July 11, 1950, to Zenko, shows a hand truck incorporating a hoist to facilitate the loading and unloading thereof. The hoist comprises a platform connected to the piston of a hydraulic cylinder. The hydraulic cylinder is actuated for raising the platform. U.S. Pat. No. 2,881,865, issued Apr. 14, 1959, to Lewis, shows a hand truck having a crank operated platform on the front thereof. U.S. Pat. No. 2,981,374, issued Apr. 25, 1961, to Holsclaw, shows a hand truck having a pair of laterally spaced channel bars which accept wheels mounted on a vertically displaceable platform. A pair of cables are attached to the platform at one end and are wound around separate spools disposed at the top of the hand truck. The spools are connected to a common shaft which is rotatable by a crank. A brake is also provided for holding the platform at a desired vertical position. U.S. Pat. No. 3,476,212, issued Nov. 4, 1969, to Eakins, shows a stepladder having a vertically movable platform for lifting work to the top of the stepladder. The platform is raised through rotation of a crank. The crank is connected to a worm which rotates a worm gear causing a chain and sprocket drive to lift the platform. U.S. Pat. No. 3,490,558, issued Jan. 20, 1970, to Foley, shows a stepladder scaffold apparatus wherein a stepladder is connected atop a platform having four wheels to facilitate movement of the apparatus. The stepladder itself contains several platforms, the position of which can be adjusted vertically on the stepladder.